The invention relates to rotary internal combustion engines of the type disclosed in U.S. Pat. No. 2,988,065 granted June 13, 1961 to Wankel et al. In engines of this type the engine working chambers rotate with the engine rotor and as a result unburnt fuel tends to accumulate in the trailing portion of each working chamber from which it is discharged into the engine exhaust port. This problem has been recognized in U.S. Pat. No. 3,393,666 granted July 23, 1968 to Yamamoto et al. In this latter patent, grooves are provided in the engine trochoid surface of the rotor housing in the region in which combustion takes place so that when a rotor apex seal passes over the grooves, the pressure differential across the apex seal blows unburnt fuel into the following working chamber whereby those unburnt gases, in effect, are recycled in the engine. Copending application, Ser. No. 695,046 filed June 11, 1976 now U.S. Pat. No. 4,040,392 by applicant's assignee on an invention of Woodier, discloses an improvement over the Yamamoto et al. arrangement but being similar in that grooves are provided in the trochoid surface of the rotor housing.
A substantial portion of the unburnt combustion gases tend to collect in the narrow or crevice-like space between the rotor and side housings radially outwardly of the rotor gas seals adjacent to the trailing portion of a working chamber during its expansion phase. The arrangement disclosed in the Yamamoto et al. patent and in the copending application of Woodier does not serve to scavenge this crevice-like space of unburnt gases.